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Re: [PATCH v2] compiler.h: Don't use compile-time assert when __NO_INLIN

From: Richard Henderson
Subject: Re: [PATCH v2] compiler.h: Don't use compile-time assert when __NO_INLINE__ is defined
Date: Sat, 15 Feb 2020 19:21:17 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1

On 2/5/20 6:15 AM, Zenghui Yu wrote:
> Our robot reported the following compile-time warning while compiling
> Qemu with -fno-inline cflags:
> In function 'load_memop',
>     inlined from 'load_helper' at /qemu/accel/tcg/cputlb.c:1578:20,
>     inlined from 'full_ldub_mmu' at /qemu/accel/tcg/cputlb.c:1624:12:
> /qemu/accel/tcg/cputlb.c:1502:9: error: call to 'qemu_build_not_reached' 
> declared with attribute error: code path is reachable
>          qemu_build_not_reached();
>          ^~~~~~~~~~~~~~~~~~~~~~~~
>     [...]
> It looks like a false-positive because only (MO_UB ^ MO_BSWAP) will
> hit the default case in load_memop() while need_swap (size > 1) has
> already ensured that MO_UB is not involved.
> So the thing is that compilers get confused by the -fno-inline and
> just can't accurately evaluate memop_size(op) at compile time, and
> then the qemu_build_not_reached() is wrongly triggered by (MO_UB ^
> MO_BSWAP).  Let's carefully don't use the compile-time assert when
> no functions will be inlined into their callers.
> Reported-by: Euler Robot <address@hidden>
> Suggested-by: Richard Henderson <address@hidden>
> Signed-off-by: Zenghui Yu <address@hidden>
> ---
> v2 is actually written by Richard Henderson.
> v1: https://lore.kernel.org/r/address@hidden
>  include/qemu/compiler.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Queued to tcg-next.


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